#include <iostream>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <cstdio>
#include <cstring>

void ChildWrite(int wfd)
{
    char buffer[1024];
    int cnt = 0;
    while(true)
    {
        snprintf(buffer,sizeof(buffer),"i am child say %d,cnt: %d",getpid(),cnt++);
        write(wfd,buffer,strlen(buffer));
        sleep(1);
    }
}

void FatherRead(int rfd)
{
    char buffer[1024];
    while(true)
    {
        buffer[0] = 0;
        ssize_t n = read(rfd,buffer,sizeof(buffer)-1);
        if(n > 0)
        {
            buffer[n] = 0;   //buffer[n] = '\0'
            std::cout << buffer << std::endl;
        }
        
    }
}
int main()
{
    //1.创建管道
    int fds[2] = {0};      //管道描述符数组,fds[0]:读端，fds[1]:写端
    int n = pipe(fds);     //管道创立成功返回0，失败返回-1，错误码被创立
    if(n < 0)
    {
        std::cout << "pipe error" << std::endl;
        return 1;
    }

    std::cout << "fds[0]= " << fds[0] << std::endl;
    std::cout << "fds[1]= " << fds[1] << std::endl;

    //2.创建子进程
    pid_t id = fork();
    if(id == 0)
    {
        //child
        //3.关闭不需要的读写端，形成通信信道
        // f -> r,  c -> w
        close(fds[0]);
        ChildWrite(fds[1]);
        
        close(fds[1]);
        exit(0);
    }

    //3.关闭不需要的读写端，形成通信信道
    // f -> r,  c -> w
    close(fds[1]);
    FatherRead(fds[0]);
    waitpid(id,nullptr,0);  //等待子进程
    close(fds[0]);
    return 0;
} 
